title: Voyager 1 observes low-energy galactic cosmic rays in a region depleted of heliospheric ions.
abstract: On 25 August 2012, Voyager 1 was at 122 astronomical units when the steady intensity of low-energy ions it had observed for the previous 6 years suddenly dropped for a third time and soon completely disappeared as the ions streamed away into interstellar space. Although the magnetic field observations indicate that Voyager 1 remained inside the heliosphere, the intensity of cosmic ray nuclei from outside the heliosphere abruptly increased. We report the spectra of galactic cosmic rays down to ~3 × 10(6) electron volts per nucleon, revealing H and He energy spectra with broad peaks from 10 × 10(6) to 40 × 10(6) electron volts per nucleon and an increasing galactic cosmic-ray electron intensity down to ~10 × 10(6) electron volts.
authors.affiliation: California Institute of Technology, Pasadena, CA 91125, USA. ecs@srl.caltech.edu
authors.forename: E C
authors.initials: EC
authors.lastname: Stone
authors.forename: A C
authors.initials: AC
authors.lastname: Cummings
authors.forename: F B
authors.initials: FB
authors.lastname: McDonald
authors.forename: B C
authors.initials: BC
authors.lastname: Heikkila
authors.forename: N
authors.initials: N
authors.lastname: Lal
authors.forename: W R
authors.initials: WR
authors.lastname: Webber